1. Field of the Invention
The present invention relates to a substrate processing apparatus and method for processing substrates, such as semiconductor wafers by a plurality of processes including a cleaning process and drying process.
2. Description of the Related Art
A semiconductor device fabricating process employs a processing apparatus that cleans substrates, such as semiconductor wafers (hereinafter referred to simply as "wafers") to remove a resist film formed on the wafers for a photolithographic process, and contaminants adhering to the wafers, such as particles organic substances and metallic impurities, from the wafers. Widely known conventional processing apparatuses of this type are of batch processing systems that clean and dry a plurality of wafers in a batch.
Such a processing apparatus is provided with a wafer processing unit, a rinsing unit and a wafer drying unit. The wafer processing unit processes wafers by supplying process gases and steam into a processing chamber. The rinsing unit immerses wafers in pure water contained in a cleaning tank for rinsing (rinsing process). The wafer drying unit dries wafers by supplying isopropyl alcohol (hereinafter abbreviated to "IPA") into a drying chamber. Processed wafers are subjected sequentially to a rinsing process and a drying process.
An ozone-assisted process is carried out for altering resist films formed on wafers by using, for example, ozone gas (O.sub.3 gas) and steam into water-soluble films that can be easily removed from the wafers by a subsequent rinsing process. A hydrofluoric acid cleaning process for removing an natural oxide film and contaminants from wafers uses hydrofluoric acid vapor (HF vapor). When carrying out a plurality of wafer processing processes by a single wafer processing apparatus, a wafer processing unit and a rinsing unit are used for each of the plurality of wafer processing processes, and the plurality of wafer processing processes and rinsing processes are carried out alternately.
However, since the conventional wafer processing apparatus is provided with an individual wafer processing unit, an individual rinsing unit and an individual wafer drying unit, the wafer processing apparatus is large. When carrying out a plurality of processes by a plurality of processing units included in a single processing apparatus, the processing apparatus must be provided with a plurality of wafer processing units and a plurality of rinsing units. Consequently, the processing apparatus needs a large floor space for installation. Wafers processed by a process using a mixture of a processing gas and steam are carried to a rinsing unit. While the wafers are being carried to the rinsing unit, the wafers are exposed to the atmosphere, which is undesirably because the exposure of the wafers to the atmosphere the possibility of formation of a natural oxide film on the wafers. If carrying the wafers to the rinsing unit takes a long time, reaction products produced on the wafers by the process using the mixture of the processing gas and steam and deteriorated films formed on the wafers are changed into the different matters when the same are exposed to the atmosphere. Consequently, it is possible that the reaction products and films which are expected to be easily rinsed off the wafers by a subsequent rinsing process are hardened or become insoluble and remain as contaminants on the wafers.